Interim Guidance for UAT Avionics Operating with Safe Flight 21 ...

3 Report Interface Guidance
3.1 Background
This Section provides an example report interface format for the UAT equipment.
Specifically, this is the report interface between the UAT Avionics and the Application
Avionics to provide reports that are a direct result of messages received over the UAT air
interface 1 . This guidance is targeted primarily for general aviation implementations to
foster an open report output interface for UAT radio equipment
This Section describes a reference interface comprising a set of application-level reports
that are constructed using a standardized packet format. Also presented is an example of
this interface with link-layer encapsulation using frames based on an HDLC format. This
reference interface provides for delivery of received ADS-B and TIS-B traffic, ADS-B
ownship position, and FIS-B uplinks to Application Avionics.
Note: This guidance does not apply to integrated implementations where no external
interface is required.
3.2 Composing “Reports”
The UAT report assembly function is implemented as a “pipeline” for delivery of
message payloads received via the UAT Avionics and augmented with appropriate report
fields.
As indicated in Section 2.2.9 of [UAT MOPS], the Time of Message Receipt (TOMR)
field is added to the received information by the UAT equipment. TOMR has sufficient
resolution and span to resolve the time reference for the received message. Absolute
time is not necessary if the Application Avionics has access to its own absolute time
reference. The TOMR value is the high-accuracy time measurement within the current
second, which may be used by an external application for range measurement and
validation.
3.3 Report Packet Format
Table 3-1 shows the recommended definition of a report packet format and Table 3-2
shows the recommended set of report packet types.
1 The “report” interface is essentially one way from the UAT Avionics to the Application Avionics. Various required inputs to
the UAT Avionics (e.g., position, velocity, time etc) are not addressed here even though they may share the same physical
interface with the report interface.
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